title: Molecular Insights on Post-chemotherapy Retinoblastoma by Microarray Gene Expression Analysis.
abstract: OBJECTIVE
  Management of Retinoblastoma (RB), a pediatric ocular cancer is limited by drug-resistance and drug-dosage related side effects during chemotherapy. Molecular de-regulation in post-chemotherapy RB tumors was investigated.
  
  
  METHODS
  cDNA microarray analysis of two post-chemotherapy and one pre-chemotherapy RB tumor tissues was performed, followed by Principle Component Analysis, Gene ontology, Pathway Enrichment analysis and Biological Analysis Network (BAN) modeling. The drug modulation role of two significantly up-regulated genes (p≤0.05) - Ect2 (Epithelial-cell-transforming-sequence-2), and PRAME (preferentially-expressed-Antigen-in-Melanoma) was assessed by qRT-PCR, immunohistochemistry and cell viability assays.
  
  
  RESULTS
  Differential up-regulation of 1672 genes and down-regulation of 2538 genes was observed in RB tissues (relative to normal adult retina), while 1419 genes were commonly de-regulated between pre-chemotherapy and post- chemotherapy RB. Twenty one key gene ontology categories, pathways, biomarkers and phenotype groups harboring 250 differentially expressed genes were dys-regulated (EZH2, NCoR1, MYBL2, RB1, STAMN1, SYK, JAK1/2, STAT1/2, PLK2/4, BIRC5, LAMN1, Ect2, PRAME and ABCC4). Differential molecular expressions of PRAME and Ect2 in RB tumors with and without chemotherapy were analyzed. There was neither up- regulation of MRP1, nor any significant shift in chemotherapeutic IC50, in PRAME over-expressed versus non-transfected RB cells.
  
  
  CONCLUSIONS
  Cell cycle regulatory genes were dys-regulated post-chemotherapy. Ect2 gene was expressed in response to chemotherapy-induced stress. PRAME does not contribute to drug resistance in RB, yet its nuclear localization and BAN information, points to its possible regulatory role in RB.
authors.affiliation: Larsen and Toubro Department of Ocular Pathology, Vision Research Foundation, Sankara Nethralaya, Chennai, India. ; Birla Institute of Technology and Science (BITS), Pilani, India.
authors.forename: Venkatesan
authors.initials: V
authors.lastname: Nalini
authors.forename: Ramya
authors.initials: R
authors.lastname: Segu
authors.forename: Perinkulam Ravi
authors.initials: PR
authors.lastname: Deepa
authors.forename: Vikas
authors.initials: V
authors.lastname: Khetan
authors.forename: Madavan
authors.initials: M
authors.lastname: Vasudevan
authors.forename: Subramanian
authors.initials: S
authors.lastname: Krishnakumar
keywords: Ect2; MYBL2; NCoR1; PRAME; RB; chemotherapy; drug resistance; micro array